Analyzing the Behavior of Hybrid Steel System of Tube in Tube with Bracing and Belt Truss

Nowadays, due to the escalation in construction of high-rise structures, the need for selecting a proper resistant structural system against earthquake and wind has increased significantly. These systems should show an optimized use of materials and should be presented as a hard and efficient structure. A good example of a high efficient system in high-rise buildings can be indicated is, the tubular system that was introduced by Fazlur Khan for the first time. It has been applied in most tall buildings all over the world. The major weakness of these systems is shear lag which restricts the column capacity from functioning properly. An appropriate solution to resolve this problem is using a braced tube system. Also, because of increasing height of the structure, the use of braced tube structures alone is not effective to control the lateral structures. Therefore, a combination of the braced tube with the inner tube and belt truss is more efficient. This paper focuses on the behavior of the hybrid steel system of tube in tube with bracing and belt trusses. To this aim, some buildings were modeled with different structural systems and different number of stories and were analyzed in terms of shear lag in web and flange, lateral displacement and drift, and absorption percent of shear force under earthquake forces. From the results obtained, it can be concluded that the belt truss does not have a favorable impact on the shear lag in the flange, but it reduces drift significantly. In addition, by adding external bracing to tube in the tube structure with belt trusses, the performance of structure improved remarkably in the aspect of shear lag, lateral displacement and absorption percent of the shear force .